The present invention relates to a method for determining the compaction state of a subgrade to be compacted by means of a roller compactor having at least one compactor drum rotatable about an axis of rotation.
In order to compact a subgrade such as for the application of pavement in road construction, roller compactors are used which, using the weight of their footprint exerted in an essentially vertical direction by one or more compactor drums, enable the compression of the subgrade and, consequently, an increase in the degree of compaction. In order to improve the compaction result, it is known to associate one or more compactor drums of a roller compactor with an oscillation-inducing arrangement, which, due to the generation of periodically oscillating torque, the compactor drum will be put into a corresponding periodic oscillating motion or rather oscillating rotation, meaning an alternating reciprocal motion around the rotational axis of the drum. Given the rotational motion of the compactor drum inherently present with the forward motion of the roller compactor, this oscillating rotation of the compactor drum will be transferred to the rotational axis of the compactor drum.
From DE 35 90 610 C2, the deduction of a degree of compaction is known given the progress over time of the oscillating torque generated in a compactor drum created by the generation of an oscillating rotation, specifically the measured horizontal acceleration of the compactor drum's axis.
DE 37 07 684 C2 discloses a method for determining the degree of compaction of a subgrade to be compacted using a compactor drum. This method measures the vertical acceleration of a compactor drum set into vertically vibrating motion by a vibrating arrangement. Since the vertical movement of the compactor drum changes as the level of compaction increases, the trend in the vertical acceleration of the compactor drum can be used to provide an indication of the compaction state of a subgrade to be compacted.